Nanotechnology is a optimistic field in terms of environmental improvements including energy savings and reduced reliability on non-renewable resources, as well as reduced waste, toxicity and carbon emissions. Alumina component reacts with calcium hydroxide produced from the hydration of calcium silicates. The rate of the pozzolanic reaction is proportional to the amount of surface area available for reaction. Therefore, it is possible to add nano- Alumina of a high purity and a high Blaine fineness value in order to improve the characteristics of cement mortars The Aim of this project is to devlope the nano concrete and to study the effects of nano alumina on the properties of concrete. In this investigation the cement is replaced by 10% Fly-ash and Alumina nanoparticles of different proportion i.e 0.5%, 1%, 1.5%, 2.0%, 2.5% & 3% in M40 grade of concrete. It is observed that workability decreased with replacement of cement. The compressive strength of nano concrete casted by partially replacement of 10% fly ash & 2% & 2.5% colloidal nano alumina , increased over conventional concrete about 18.03%, 14.28% for 3 days and 12.7%, 11.27% for 7 days and 4.17% , 2.07% for 28 days. The Split Tensile strength of this concrete increases with 5.73% and 9.16% respectively over conventional concrete for the replacement 1.5% and 2%. Flexural strength of this concrete increases with 13.05% and 26.65% over conventional concrete for the replacement 2% and 2.5%.